He came to the throne while much of Europe was moving towards domination by all-powerful monarchs, such as Louis XIV of France. Charles would attempt to pursue similar policies but would be limited by a robust parliamentary opposition. There was widespread opposition to many of Charles' actions. These included the use of the Court of the Star Chamber to suppress dissent; a policy of taxation without the approval of Parliament; and a religious policy that was seen by the Puritans as attempting to bring the Anglican Church closer to Roman Catholicism.

Although the marriage seems to have been a successful one, it was never popular with the British people.

Conflict with Parliament became intense over the issue of the Huguenots. The expedition to relieve La Rochelle under Buckingham had been disastrous. The Commons passed resolutions against arbitrary taxes, and arbitrary arrest, and passed the Petition of Right. Buckingham was assassinated by John Felton[?] on August 23, 1629. Parliament tried to pass further motions obnoxious to the king, and was dissolved on March 29, 1629.
The years that followed were called the eleven years' tyranny. Charles was barely able to keep government functioning without further taxes being voted, and was forced to rely on inventive methods of raising finance. One of these was ship money.

After the death of Buckingham, two new men assumed growing importance in the government: Thomas Wentworth, Earl of Strafford and William Laud. Laud, made archbishop of Canterbury, was instrumental in a policy of imposing a strict conformity on the Church: but it was a conformity in line with his Arminianism, and was met with continued hostility by the Puritans. England, however, remained quiet and even prosperous, until Charles tried in 1637 to impose this same conformity on the Scots.

The result was the revival of the National Covenant and the first of the Bishops' Wars, which ended in a humiliating truce for Charles on June 18, 1639. It was in order to raise money to subdue the Scots that he was forced to take the fateful step of recalling Parliament in April 1640. This Short Parliament proved unamenable to Charles's wishes, and was dissolved on May 5. After another defeat in Scotland, Charles was once again persuaded to recall Parliament.

This Long Parliament soon brought matters to a head, and took measures which both threatened Charles's political position and caused him deep personal grief. Wentworth was impeached, and, that having failed, executed by bill of attainder. Laud was imprisoned. Charles was forced into one concession after another - the affirmation of Presbyterianism in Scotland and the abolition of ship money and the Star Chamber. But he could not agree to the Militia Bill, which would have taken control of the army from him. The threat of this and attacks on Henrietta Maria, led him to try and seize control of events by seizing the persons of five members of Parliament identified as the key ringleaders. By violating Parliament with an armed force, he made the breach permanent. It was no longer safe for him to be in London, and he went north; the Queen went abroad.

The English Civil War had not yet started, but both sides began to arm. After futile negotiations Charles raised the royal standard (an anachronistic medieval gesture) in Nottingham on August 22, 1642.
Charles set up court at Oxford, from where his government controlled roughly the north and west of England, Parliament remaining in control of London and the south and east. The war went on indecisively through 1643 and 1644, until the Battle of Naseby tipped the miliary balance desively in favour of Parliament. There followed the Siege of Oxford[?], from which Charles escaped in April 1646. He put himself into the hands of the Scottish Presbyterian army at Newark, who delivered him to Parliament as part of a deal in January 1647. He was imprisoned at Holdenby House in Northamptonshire, until cornet George Joyce[?] took him by force to Newmarket in the name of the army. At this time, mutual suspicion had developed between the army and Parliament, a suspicion that Charles was eager to exploit.

He was then transferred first to Oatlands and then to Hampton Court, where more involved but fruitless negotiations went on. He was persuaded that it would be in his best interests to escape - perhaps abroad, perhaps to France, or perhaps to the custody of Robert Hammond[?], Parliamentary governor of the Isle of Wight. He decided on the last course, believing Hammond to be sympathetic, and fled on November 11. Hammond, however, was appalled and confined him in Carisbrooke Castle[?].

Here he continued to try and bargain with the various parties, eventually coming to terms with the Scottish Presbyterians that he would allow the establishment of Presbyterianism in England as well as Scotland for a trial period. The Royalists rose in July 1648, and the Scots invaded. When the Scottish armies were finally defeated at the Battle of Preston, pressure grew in the army for Charles to be put on trial.

This was a novel idea; monarchs had been deposed before, but never brought to trial as monarchs. The leaders of the plan to execute the king (the result of the trial being a foregone conclusion), were determined that this would be no act done in a corner, and Charles was tried in his person as King of England. On January 20, 1649, the trial began. Many of the famous names of the opposition to his name refused to have any part in it; he was tried by an illegal parliament of 135 members. His trial lasted from January 19 to January 27, 1649. He was convicted of treason against the state by 68 votes that found him guilty to 67 votes for acquittal. Some sources claim that the deciding vote belonged to Cromwell who chose to vote last. Charles was beheaded on January 30, 1649 by Richard Brandon, a professional hangman. His death warrant refers to him as "Charles Stuart, King of England".

At his trial, "I demand to know by what authority, I mean lawful authority I am called here. Remember, I am your King, your lawful King. And what sins you bring upon your heads, and the judgement of God upon this land, think well upon it, before you go from one sin to a greater one. I have a trust committed to me by God, by lawful inheritance. I will not betray it to answer to a new and unlawful authority." [1] (http://www.autodidactproject.org/other/PKCS)

A subject and a sovereign are clean different things. If I would have given way to an arbitrary way, for to have all laws changed according to the Power of the Sword, I needed not to have come here, and therefore I tell you ... that I am the martyr of the people.